Fix hfsplus oops on image without extents

Fix an oops with a corrupted hfs+ image.

See http://bugzilla.kernel.org/show_bug.cgi?id=10548 for details.

Problem is that we call hfs_btree_open() from hfsplus_fill_super() to set
HFSPLUS_SB(sb).[ext_tree|cat_tree] Both trees are still NULL at this moment.
If hfs_btree_open() fails for any reason it calls iput() on the page, which
gets to hfsplus_releasepage() which tries to access HFSPLUS_SB(sb).* which is
still NULL and oopses while dereferencing it.

[akpm@linux-foundation.org: build fix]
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/hfsplus/inode.c b/fs/hfsplus/inode.c
index d53b2af91c25..67e1c8b467c4 100644
--- a/fs/hfsplus/inode.c
+++ b/fs/hfsplus/inode.c
@@ -65,6 +65,8 @@ static int hfsplus_releasepage(struct page *page, gfp_t mask)
                 BUG();
                 return 0;
         }
+        if (!tree)
+                return 0;
         if (tree->node_size >= PAGE_CACHE_SIZE) {
                 nidx = page->index >> (tree->node_size_shift - PAGE_CACHE_SHIFT);
                 spin_lock(&tree->hash_lock);